Blank firing attachment for firearms



April 29, 1969 B. R. SAWYER BLANK FIRING ATTACHMENT FOR FIREARMS Sheet Filed March 17, 1967 mm on a mm X 3 N W BM ATTOE/VEYJ April 29, 1969 s w R 3,440,924

BLANK FIRING ATTACHMENT FOR FIREARMS Filed March 17, 1967 Sheet 2 of 4 Y1 FIG. 5.

B R. SAWYER @n an,

A TTOZ/VEJU April 29, 1969 B, SAWYER 3,440,924

BLANK FIRING ATTACHMENT FOR FIREARMS Filed March 17, 1967 Sheet 3 of 4 FIG. u.

DVVE/VTOE B R SAWYER ATTOJWZ'YY April 29, 1969 B. R. SAWYER BLANK FIRING ATTACHMENT FOR FIREARMS Sheet Filed March 17, 1967 m a m N ZNVEIVTOZ B R SAWYER Qj/ m, W

ATTQEKE'YI United States Patent 0 3,440,924 BLANK FIRING ATTACHMENT FOR FIREARMS Benyamrn Robinson Sawyer, Waltham "Cross, England, assignor to The Secretary of State for Defence in Her Britannic Majestys Government of the United Kingdom of Great Britain and Northern Ireland, London, England Filed Mar. 17, 1967, Ser. No. 624,069 Claims priority, application Great Britain, Mar. 17, 1966, 11,684/66; Jan. 27, 1967, 4,159/67 Int. Cl. F41f 17/02, 1.7/08; F41c 21/00 US. Cl. 8914 18 Claims ABSTRACT OF THE bIscLosURE A blank firing attachment for restricting the flow of gas from the muzzle of a weapon when firing blank ammunition and comprising an extension tube incorporating a construction, a barrel attachment for attaching the tube to the muzzle of the weapon in alignment with its bore and means for locking the attachment in position.

This invention relates to firearms and is concerned with attachments for mounting on the muzzles of firearms when firing blank ammunition. Such attachments will, hereinafter, be referred to as blank firing attachments, and when references made to a weapon, it will be understood that a firearm type of weapon is intended.

When blank ammunition is being used in a gas operated, automatic weapon, the back pressure of the propellant gases, passing through an unobstructed bore, is usually insuflicient to operate the automatic firing mechanism and, consequently, the weapon cannot, without modification, be fired automatically. To overcome this difficulty, blank firing attachments have previously been proposed incorporating a spigot arranged to enter a short distance into the muzzle end of the weapon bore wich is thereby constricted to an annular gap between the spigot and the barrel. The back pressure of the propellant gases is thus increased, enabling the weapon to operate automatically. The attachment has, in some cases, been mounted by means of a leaf spring extending alongside the barrel to engage a bayonet stud and, in others, by means of a threaded attachment adapted to mate with, for example, a part of a fiash hider. This type of blank firing attachment has the disadvantage that the bore, in the vicinity of the constriction becomes fouled by hard carbonaceous deposits which are ditficult to remove, and the continual scraping which is necessary for their removal tends to damage the bore and cause inaccuracy. The leaf spring type of attachment has the further disadvantage that the spring tends to weaken, or even to break, after continuous use, with undesirable results.

These disadvantages are overcome by the present invention which comprises a blank firing attachment including an extension tube in which is incorporated a constriction; a barrel attachment for attaching the tube to the muzzle of a weapon in alignment with the bore thereof; and means for locking the blank firing attachment in position on the weapon.

Preferably the tube and the barrel attachment are relatively movable to facilitate alignment of the tube and location of the barrel attachment in position relative to the weapon muzzle. A preferred form of blank firing attachment therefore comprises an extension tube incorporating a constriction; a barrel attachment for attaching the tube to the muzzle of a weapon in alignment with the bore thereof, the tube and the barrel attachment being relatively movable to facilitate attachment; and means for locking the blank firing attachment in position on the muzzle.

The relative movement may be purely rectilinear axial movement or purely articulation or may be a combination of axial movement and articulation. In one particularly preferred form of device, the relative movement between the extension tube and the barrel attachment is achieved by means of co-operating screw-threads on the two members whereby relative axial movement can be produced, which screw-threads can be disengaged to permit relative articulation. The barrel attachment may incorporate means for engaging a rearwardly facing lateral surface, fixed relative to the barrel of the weapon, the co-operating screwthreads being used to screw the extension tube firmly into engagement with the muzzle after the attachment has been placed in positionJPos'itioning of the attachment may be facilitated by its articulation relative to the tube. If a fiash hider is fitted to the weapon, as is usually the case with modern weapons, the blank firing attachment may be fitted over it, the extension tube being long enough to reach the barrel, through the fiash hider, on or over which the barrel attachment is mounted. If no flash hider is fitted the whole attachment may be considerably shorter and attached directly to the barrel.

The constriction in the extension tube may be, simply, a reduction in its internal diameter or may be formed by use of a cross pin traversing the tube diametrally, which pin may be removable to facilitate cleaning.

The above, improved devices, although safer than previously known forms of blank firing attachment, still present the occasional hazard due to flying debris, comprising parts of the attachment and the bullet, should a live round be inadvertently fired through the attachment. In order to overcome this objection, a further improved form of blank firing attachment in accordance with the invention incorporates means for arresting and retaining a bullet fired from the weapon to which it is attached. At the forward end of the extension tube is incorporated an elongated constriction within a casing of sufficiently robust construction to withstand the impact of a bullet and to prevent egress of the bullet or any major portion of the bullet therefrom. Preferably there is provided, at or near the forward end of the extension tube and within said casing, a separate, deformable tubular arrestor, coaxial with the extension tube and whose bore includes at least part of the constriction, which tubular arrestor is arranged to buckle on impact of a bullet with its rear end whereby its bore is distorted to prevent extrusion of bullet material therethrough. Deformation of the tubular member also serves to absorb bullet energy thus assisting in bringing the bullet to rest and enabling it to be retained within the casing.

Various forms of blank firing attachment in accordance with the invention will now be particularly described, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 is a longitudinal section of one form of the device,

FIG. 2 is a longitudinal section of a second form of the device,

FIG. 3 is a transverse section on the line III-III of FIG. 2,

FIGS. 4 and 5 are longitudinal sections of third and fourth forms of the device,

FIG. 6 is a transverse section on the line VIVI of FIG. 5,

FIG. 7 is a longitudinal section of a fifth form of the device,

FIGS. 8 and 9 are, respectively, a longitudinal section and a longitudinal elevation of a sixth form of the device,

FIG. 10 is an axial view in the direction of arrow X of the lock sleeve 92a shown in FIG. 11,

FIG. 11 is a longitudinal section of a modified form of the device shown in FIG. 8,

FIG. 12 is a longitudinal section of a seventh form of the device,

FIG. 13 is a detail of a part of FIG. 12 as it appears after firing a live round, and

FIG. 14 is a longitudinal section of a modified form of the device shown in FIG. 12.

The orientations of the devices will, for the purposes of the following description, be those assumed when attached to a weapon in its firing position. With the exception of the device shown in FIG. 14, which is adapted to fit directly onto the weapon barrel, all the devices described and illustrated are intended to be fitted over a flash hider already attached to the muzzle of the weapon.

In the first form to be described (FIG. 1), the extension tube 1 has a main bore 2 of slightly less than the weapon bore diameter, its rear end being externally chamfered 3 to seat just into the muzzle end of the bore of the weapon 4 or, as shown, of a collar 5 attached to the muzzle. The forward end of the tube 1 carries a coaxial knurled wheel 6 to permit manipulation and, just rearward thereof, a short length of external screw-thread 7. Within the forward end of the tube is formed a venturi shaped constriction 8. For ease of manufacture, the wheel portion 6 may be made separately with a short hollow stem 9 which carries the screw-thread 7 and the venturi 8, the remainder of the tube 1 being force fitted into a counterbore 10 in the rear end of the stem 9. The barrel attachment 11 is a tube of larger diameter whose rear end fits over a flash hider 12 fitted onto the barrel of the weapon 4 and carries a lateral lug 13, incorporating a spring catch 14, which engages the bayonet stud 15 to secure the attachment 11 firmly in position. The forward end of the barrel attachment 11 has, formed therein, a conical seating 16 immediately rearward of which is an internal screw-thread 17 into which the extension tube 1 can be screwed. Mounted on the screw-thread 7 of the extension tube 1 between the barrel attachment 11 and the knurled wheel 6 is a locking member 18 consisting of a stem 19 in the form of a split collet which can be screwed into the conical seating 16 of the barrel attachment 11 by manipulation of a knurled flange 20 carried by the stem 19. To attach this blank firing attachment, the barrel attachment 11 is pushed into position, over the fiash hider .12, until the spring catch 14 holds it firmly by engagement with the bayonet stud 15. The extension tube 1 is screwed in until its inner end seats firmly in the collar 5 whereupon the locking member 18 is screwed into its seating 16 to compress the collet jaws of the stem 19 radially to lock the device in position. This device is quite effective in action but the venturi type orifice 8 is difficult to clean and the more positive locking devices used in the following forms of blank firing attachments are considered preferable to this collet device.

In the second form of blank firing attachment (FIGS. 2 and 3) the extension tube 21 is of similar internal diameter and fits, in the same way, into the end of the weapon bore or the collar 5. The constriction, however, is formed, near the forward end, by the insertion of a cross pin 22 diametrally of the tube 21, which pin 22 is lightly held in position by a helical spring 23 in compression between a shoulder 24 formed on the tube 21 and the ends of the pin 22 which protrude radially beyond the outer surface of the tube 21. This tube 21 also has a part of its length externally screw-threaded at 25 but does not have a knurled wheel as in the first form described. The barrel attachment 26 is similar to that of the first form of attachment and is mounted over the flash hider 12, in the same manner. The forward end however has, in place of the conical seating 16 (FIG. 1), a cylindrical counterbore 27, in which is mounted a helical, lock sleeve spring 28, and is also provided with a ring of radially extending external teeth 29. The locking means consists of a lock sleeve 30 mounted on the forward end of the extension tube 21, around the cross pin 22 whose protruding ends engage in longitudinal slots 31 in the inner surface of the sleeve 30 so that the sleeve 30 can be used to rotate the extension tube 21. The rear end of the sleeve 30 has a counterbore 32, at the rear end of which are formed internal radial teeth 33, which counterbore 32 also accepts the forward end of the lock sleeve spring 28. The slots 31 in which the ends of the cross pin 22 engage, extend from the forward face of the sleeve 30 but terminate at an intermediate point of its length to limit forward movement of the sleeve 30 on the extension tube 21.

This attachment is fitted by pushing the barrel attachment 26 into position on the barrel as before until the spring catch 14a in lug 13a engages the bayonet stud 15, the extension tube 21 with the lock sleeve 30 in position then being screwed into the barrel attachment 26 by rotation of the lock sleeve 30, compressing the lock sleeve spring 28. Before the tube '21 engages the collar 5 the in ternal teeth 33 on the sleeve 30 are brought longitudinally into alignment with the external teeth 29 on the barrel attachment 26. In order to complete the insertion of the extension tube 21, the sleeve 30 is pressed rearward against the action of the lock sleeve spring 28 until the teeth 29, 33 move longitudinally out of engagement, when the sleeve 30 may be rotated to screw in the extension tube 21. On final release of the sleeve 30 the teeth 29, 33 re-engage to lock the attachment very firmly in position. The outer surface of the sleeve 30 may be knurled 34 for easy manipulation.

These first two types of attachment employ only relative axial movement of the barrel attachment and the extension tube. The third (FIG. 4), now to be described, employs only relative articulation. The extension tube 35 in this case, incorporates the cross pin constriction 36 with a retaining spring 37, as in the second form described but has no external screw-thread. The barrel attachment 38 comprises a channel member 39 having, near its forward end, a pair of bearings 39a in which are journalled the protruding ends of the cross pin 36 which thus forms a pivotal connection. At the rearward end of the channel member is a bridge block 40 extending across the channel, between a pair of lateral extensions 41 of the sides of the channel 39. The block 40 is drilled and screw-threaded to carry a lock screw 42 which extends obliquely through the block 40 forwardly toward the channel 39. To fit this attachment, the rear end of the channel 39 is placed in position over the flash hider (not shown) which enters between the base of the channel 39 and the bridge block 40 until the latter is positioned just rearward of the bayonet stud. The rear end of the extension tube 35 will then be adjacent its seating on the muzzle face or collar. The tube 35 can be aligned by rotation about the cross pin 36 whereafter the attachment is locked by screwing the lock screw 42 into engagement with the rear face of the bayonet stud. To avoid loosening under vibration, the lock screw tip 43 is generally conical in form, having a series of flats 44 formed thereon to prevent the screw 42 from working loose.

The extension tube 45 of the fourth form of blank firing attachment (FIGS. 5 and 6) is similar to that of the second form, having a cross pin constriction 46 and retaining spring 47, and, rearward thereof a part of its length is externally screw threaded at 48. The extreme forward end however has a radial flange 49 on its outer surface. The barrel attattachment 50 consists of a rectangular channel member having a slot 51 in its base, near the rear end, for engaging the bayonet stud, and a transverse wall 52 at its forward end. The transverse wall 52 is bored and carries an internally screw-threaded bush 53 having a flange 54 which engages the rear face of the transverse wall 52 with the bush 53 extending forwardly through the wall. The bush is retained by a strip bent to form a U-shaped member 55 one leg 56 of which engages the rear face of the bush 53 and has a bore aligned with that of the bush. The U member 55 extends forwardly, over the transverse wall 52, and down across the axis of the bush, the assembly being held in position by a helical spring 57 surrounding the forward part of the bush 53 and in compression between the transvers wall 52 and the forward leg 58 of the U member 55. The forward leg 58 of the U member has a large orifice coaxial with the bush 53, the periphery of the orifice being formed (FIG. 6) with a series of radial notches 59. A sleeve 60 mounted on the forward end of the extension tube and retained by its flange 49, has longitudinal slots 61 in its inner surface which engage the protruding ends 62 of the cross pin 46 so that the sleeve 60 can be used to rotate the tube 45 but is capable of sliding axially thereon.

To assemble this attachment on the weapon the channel member 50 is engaged on the bayonet stud, the extension tube 45, which may already be screwed partly into the bush, 53, being now aligned with the bore and screwed in until it engages its seating in the muzzle or collar. The dimensions are such that when correctly mounted the cross pin 46 will have moved rearward to the position where its protruding ends 62 engage the notches 59 in the forward leg 58 of the U member 55. This provides an effective lock against inadvertent movement but the notches 59 may be disengaged when desired by pressing the sleeve 60 rearward to move the U member 55 against its spring 57.

The fifth and sixth types (FIGS. 7, 8 and 9) are identical in principle and differ only slightly in construction, chiefly in respect of the shape of the barrel attachments. In each case the extension tube 63, 73 incorporates a constriction formed by a cross pin 64, 74 whose ends protrude radially from the tube which also has an externally screwthreaded portion 65, 75 rearward of the cross pin 64, 74 and a radial flange 66, 76 rearward of and spaced from the threaded portion. The barrel attachments 67 of the fifth type (FIG. 7) is a trough member formed from a tube the upper side of which is cut away from the rear end to a point near the forward end. The forward end has a short complete tubular portion 68 terminating in a thick transverse wall 69 which is bored and screw-threaded to accept the screw-threaded portion of the extension tube 63, the bore being too small to pass the flange 66 on the extension tube 63. The trough has a slot 70 in its base near its rear end for engagement with the bayonet stud of the weapon. The forward face of the transverse wall 69 carries a ring of ratchet teeth 71 extending forwardly therefrom. The barrel attachment 77 of the sixth type (FIGS. 8, 9) is shorter and has an increased diameter toward its rear end. one side being cut away at 72 to a point near its forward end forward of which is a short, complete tubular portion 78 and, instead of the slot for engaging a bayonet stud, this attachment has, at its rear end, an inwardly extending flange 80 for engagement with a groove or flange on a flash hider. This attachment has a transverse wall 79 with a screw-threaded bore and ratchet teeth 81, similar to that of the fifth type.

In each of the fifth and sixth types the blank firing attachment is first assembled by screwing the extension tube 63, 73 into the barrel attachment 67, 77 from the rear and fitting a locking member to its forward end. A cup-shaped locking sleeve 82, 92 is first mounted on the forwardly protruding end of the extension tube 63, 73, its base 83, 93 rearward and adjacent the transverse wall 69, 79 of the barrel attachment 67, 77. The cylindrical wall 84, 94 of the locking sleeve 82, 92 is of sufficiently large diameter to leave an annular space between it and the extension tube 63, 73. Into this annular space is inserted an inner sleeve 85, 95 having a helical spring 86, 96 anchored to (or engaging) and extending coaxially rearward from its rear end to engage the base of the locking sleeve 82, 92. Diametrically opposite holes are formed in the walls of each of the inner sleeve 85, 95 and locking sleeve 82, 92. These holes can be brought into alignment with the cross pin holes in the extension tube 63, 73 by compressing the spring 86, 96 between the two sleeves, whereupon, insertion of the cross pin 64, 74 will retain the assembly in position, the pin being retained by the pressure thereon of the sleeves, urged by the spring. To provide a more positive retention, however, the holes 87, 97 in the locking sleeve 82, 92 are of keyhole form, the cross pin 64, 74 having ends 88. 98 of reduced diameter which, due to the action of the spring 86, 96 engage in the narrow part of the keyhole slots which will not accept the main portion of the cross pin.

To facilitate fitting of these attachments to the weapon, the screw-thread 65, 75 may be disengaged by screwing the extension tube 63, 73 forwardly until the screwthreaded orifice in the transverse wall, 69, 79 of the barrel attachment 67, 77 comes into register with a smaller diameter portion 89, 99 of the tube 63, 73 between its screwthread 65, 75 and the radial flange 66, 76. The two members (extension tube and barrel attachment) are now capable of articulation and can be correctly positioned and aligned relative to the weapon barrel. The screw-threads are now re-engagcd and the extension tube 63, 73 is screwed rearward into contact with the muzzle face or collar. During the last stages of this operation, the ratchet teeth 71, 81 on the transverse wall 69, 79 of the barrel attachment 67, 77 are engaged by similar teeth formed on the rear face of the locking sleeve 82, 92 to lock the device in position. To remove the attachment, the teeth 71, 81 may be disengaged by lifting the locking sleeve 82, 92 forward against the spring 86, 96. A modification of the sixth type of attachment is shown in FIG. 11 in which, as an alternative locking means, the 'base of the locking sleeve 92a has a ring of small holes 100 (FIG. 10) formed therein, while the barrel attachment 77a carries a peg 101 extending forwardly from the transverse wall 79a of the barrel attachment 77a, which peg 101 engages in one or other of the holes 100 to lock the device in position. This locking means can also be disengaged by lifting the locking sleeve 92a forward against the spring 96a. The device illustrated in FIG. 11 also shows a minor variation in the locking sleeve assembly, the spring 96a being of somewhat larger diameter than that shown in FIG. 8 and directly engaging the pin 74a and the locking sleeve 92a instead of being anchored to or engaging an inner sleeve (95 of FIG. 8). No inner sleeve is therefore required but the pin 74:: has two reduced diameter portions 102 in which the spring 96a locates. The barrel attachment 77a has a somewhat different external contour. Other parts of FIG. 11 which are also shown in FIG. 8 have been given the same numerals as in that figure vith suflix a.

Although the cross pin type of constriction has the advantage that it can be removed for cleaning purposes, the extension tube having a venturi type constriction, or even a simple reduction in diameter, still represents a considerable improvement over the earlier spigot type of attachment in this respect since, should the tube be come useless due to fouling or erosion, it could be fairly easily replaced without the necessity for replacement of the whole blank firing attachment. Even replacement of the whole attachment would, of course, be preferable to damaging the barrel.

The following forms of blank firing attachment incorporate means for arresting and retaining a bullet should a live round be inadvertently fired from the weapon to which it is attached and virtually eliminate the risk from flying debris in such a contingency.

The first of these forms (FIGS. 12 and 13) is designed to be fitted to a weapon carrying a flash hider.

This attachment, like those previously described, includes a barrel attachment 103, locking means 104 and an extension tube 105 incorporating a constriction 106. The extension tube 105 in this device is a three-part composite structure. At the forward end is a thick-walled, tubular casing 107 having a small bore 108 extending for a short distance from its forward end and expanding to a somewhat larger bore 109 for the major, rearward portion of its length, the two bore portions being connected by a wide-angled, conical shoulder 110. Inserted into the larger portion of the bore is a tubular arrestor 111, the forward end of which is tapered externally at a more acute angle than the internal shoulder 110 of the casing upon which it seats, so that an annular space 112 exists, bounded by the two conical surfaces and the bore surfaces of the casing 107. The rear portion of the arrestor 111, which lies wholly within the thick-walled casing 107, has a reduced external diameter. Fitted into the rear end of the casing 107 and around the rear end of the arrestor 111, is the forward end of a tubular duct 113 which extends rearwardly of the casing 107. The bore of this duct 113 is slightly maller than that of the weapon to which the attachment is to be fitted and the rear end of the duct may be chamfered to seat into, or squared off (as shown) to seat onto, the muzzle face of the weapon or the face of a collar or similar attachment to the muzzle. To retain this assembly as a composite unit, the rear end of the casing 107 is lightly brazed to the duct 113. Brazing over too large an area may, if desired, be prevented by the provision of an external groove 114 in the duct, located a short distance forward of the rear end of the casing 107, across which groove the brazing will not spread.

The forward end of the bore of the arrestor 111 has a diameter sufliciently small to increase the gas pressure, when firing blanks, to a value adequate for operating the weapon mechanism and thus constitutes the desired constriction 106. The rearward portion of the bore 115 is of somewhat larger diameter and is determined by the retarding force necessary to arrest the bullet. The relative sizes of these parts of the bore will of course depend on the weapon and ammunition being used. In some cases a uniform bore may suflice or it may sometimes be desirable to introduce more steps in the bore to graduate the retarding force.

The thick walled casing 107 carries an external screw thread 116 at its rear end, forward of which the casing has a reduced external diameter 117.

The barrel attachment 103 is a trough member in the form of a tube, the upper side of which is cut away-over about the rear two thirds of its length, leaving a complete tubular portion .118 at the forward end. The trough diameter is such that it can be fitted around the lower half of a flash hider attached to the muzzle of the weapon. The tubular portion 118 is internally threaded at its rear end to mate with the screw thread 116 on the casing 107 and, forward of the screw thread, the internal diameter is enlarged at 119. At the forward end of the tubular portion 118, a washer 120 is mounted internally, adjacent a forwardly facing shoulder and retained by a circular clip 121 engaged in an internal circumferential groove. The internal diameter of this washer 4120 is small enough to prevent the passage therethrough of the threaded portion of the casing-107 of the extension tube 105 but allows the reduced diameter portion 117 thereof to pass with some clearance. On the front end face of the barrel attachment 103 is formed a ring of ratchet teeth 122 and near the rear end of the trough portion is formed a slot 123 for engag ment with the bayonet stud of the weapon.

The attachment is assembled by screwing the composite extension tube 105 into the barrel attachment 103 and mounting on its forward end, a locking device 104. A lock sleeve 124 is fitted over the forward end of the extension tube casing 107 and is in the form of a cylindrical sleeve 124a having at its rear end a flange extending radially outward and then coaxially forward to form a forwardly facing, annular channel the outer wall of which may be provided externally with knurling 125 or other suitable gripping means. The rear face of the lock sleeve flange carries a ring of ratchet teeth for engagement with the teeth 122 on the front end face of the barrel attachment 103.

An inwardly projecting key 126 on the cylindrical sleeve 124a engages in a longitudinal keyway 127 formed in the casing 107, whereby the lock sleeve 124 can be used to rotate the extension tube 105 but the two items are capable of relative axial movement. Mounted around the cylindrical sleeve 124a is a helical lock sleeve spring 128 whose rear end is seated in the annular channel in lock sleeve 124. The forward end of the spring 128 is engaged by a cap .129 whose transverse wall 130 is bored to accept the end of the extension tube casing 107 and whose cylindrical wall extends rearwardly, its extremity lying within the outer wall of the annular channel in the lock sleeve 124 so that the spring 128 is wholly enclosed. The cap 129 is retained by a circular clip 131, forward thereof, mounted in a circumferential groove in the casing 107.

By screwing the extension tube 105 forwardly relative to the barrel attachment 103, its screw thread 116 may be disengaged and brought into register with the enlarged portion 119 of the bore of the complete tubular portion 118 of said attachment 103. In this condition, relative articulation is possible between the barrel attachment 103 and the extension tube 105. The attachment 103 can now be located in relation to the flash hider of the weapon and engaged on the bayonet stub, whereafter the extension tube 105 can be aligned with the weapon bore and screwed rearwardly into the barrel attachment 103 into engagement with the weapon muzzle or other desired seating. During the latter stages of this operation, the ratchet teeth 122 on the lock sleeve 124 and the barrel attachment 103 are brought into engagement to ensure that the device is positively locked in position. To remove the device, the teeth 122 can be disengaged by lifting the lock sleeve 124 forward against the action of the lock sleeve spring 128, whereafter the extension tube may be unscrewed.

When firing blanks, the gas flow is restricted by the small bore 106 at the forward end of the arrestor 111 to build up the required pressure for operation of the automatic mechanism. Should a live round be fired inadvert ently, the bullet, on leaving the barrel, first encounters the somewhat smaller bore of the extension tube duct 113 and some swaging of the bullet occurs with accompanying distortion of the duct and absorption of some bullet energy. The bullet, later, strikes the rear end of the arrestor 111 which distorts (as shown in FIG. 13), moving forward to fill the annular space 112 around tis forward end and buckling from the rear end to block its bore 115, thus preventing egress of any major portion of the bullet from the attachment. The bullet energy is absorbed during the above process and its distorted remains 132 are retained within the thick walled casing 107 which must, of course, be sufficiently robust to prevent bursting or otherwise breaking of the attachment on impact by the bullet. The attachment itself may be wholly or partly destroyed clue to distortion, particularly of the various parts of the extension tube 105. The danger to personnel from flying debris will, however, be eliminated.

The device shown in FIG. 14 is basically similar to that shown in FIG. 12, the rear end of the attachment having a modified form to fit onto the muzzle of a weapon 133 not fitted with a flash hider. The trough portion of the barrel attachment 103a has been shortened and, in place of a slot, is provided with an internal flange 134 to engage the bayonet mounting 135 of the weapon 133. The casing 107a of the extension tube 105a has been extended rearwardly and its rear end is shaped at 136 to provide a seating for the muzzle of the weapon 133. FIG. 14 shows a further optional modification in that the duct 113a is an integral extension of the arrestor 111a. The remainder of the construction is substantially identical with that of the device shown in FIG. 12 and certain of the major components have been accorded the same numerals as in that figure.

It will, of course, be clear to those skilled in the art that the detailed construction of this device is capable of considerable variation within the scope of the invention and.

9 that the particular form of the barrel attachment, and, to some extent, the extension tube will be influenced by the weapon and ammunition in conjunction with which the attachment is to be used. For example, although the bayonet stud is often a convenient object on which to anchor the barrel fitment, any convenient projection or groove may be used with a suitable modification to the attachment or a special attachment may be provided for the purpose. The rear end of the extension tube may be chamfered to fit into the muzzle or the bore of a collar, or it may be formed square and arranged to seat on the face of either, and the bore of the extension tube, may in some instances, be equal to or even greater than the bore of the weapon.

I claim:

1. A blank firing attachment for mounting on the muzzle of the barrel of a firearm when said firearm is firing blank ammunition, which firearm includes a seating at its muzzle and a rearwardly facing surface adjacent the muzzle, said attachment comprising an extension tube in which is incorporated a constriction for increasing the gas pressure in the barrel when firing blank ammunition; an externally threaded portion on said extension tube; a barrel attachment for attaching the extension tube to the muzzle of the firearm in alignment with the bore thereof, said barrel attachment having an internally threaded portion for engagement with the externally threaded portion of the extension tube and means for engaging the rearwardly facing surface on the firearm so as to secure the barrel attachment to the firearm; the externally and internally threaded portions of the extension tube and the barrel attachment being so arranged that the extension tube can be screwed into the barrel attachment after said attachment has been placed in engagement with the rearwardly facing surface to bring the extension tube and the barrel attachment, respectively, into tight engagement with the seating at the muzzle and the rearwardly facing surface; and locking means for preventing inadvertent relative rotation of the extension tube and the barrel attachment to avoid their unscrewing during use; the barrel attachment and the extension tube including recesses adjacent the threaded portions thereof into which said threaded portions are movable when disengaged from one another, whereby the extension tube and the barrel attachment are relatively articulable while remaining connected to one another.

2. A blank firing attachment as claimed in claim 1 incorporating means for arresting and retaining a bullet fired from the firearm to which it is attached.

3. A blank firing attachment as claimed in claim 2 wherein the bullet arresting and retaining means includes a deformable arrestor arranged to deform on the impact of the bullet therewith to absorb bullet energy and arrest the bullet.

4. A blank firing attachment as claimed in claim 2 wherein the bullet arresting and detaining means includes a tubular arrestor incorporated in and coaxial with the extension tube and whose bore is of smaller diameter than that of the firearm, said tubular arrestor being arranged to deform on impact of the bullet with its rear end, preventing egress of the bullet from the extension tube; and a tubular casing surrounding the arrestor, which casing is sufficiently robust to withstand, without breaking, the stresses imposed thereon by the impact.

5. A blank firing attachment as claimed in claim 1 for mounting on a firearm fitted with a flash hider, wherein the barrel attachment is constructed to fit over said flash hider.

6. A blank firing attachment as claimed in claim l for use on a firearm fitted with a flash hider and provided with a bayonet stud on which the rearwardly facing surface is formed, wherein the extension tube is adapted to extend internally of the flash hider to the seating at the firearm muzzle and the barrel attachment is generally tubular and adapted to be fitted over the flash hider, the means for engaging the rearwardly facing surface of the bayonet stud comprising a spring catch mounted at the rear end of the barrel attachment.

7. A blank firing attachment for mounting on the muzzle of a firearm when firing blank ammunition, which firearm has a barrel, a seating at its muzzle and a bayonet stud on which a rearwardly facing surface is formed, said attachment comprising an extension tube adapted to extend to the seating at the firearm muzzle and in which is incorporated a constriction for increasing the gas pressure in the barrel when firing blank ammunition; a generally tubular barrel attachment for attaching the extension tube to the muzzle of the firearm in alignment with the bore thereof, the barrel attachment including a spring catch mounted at its rear end for engaging the rear surface of the bayonet stud; cooperating screw-threads on the outer surface of the extension tube and the inner surface of thebarrel attachment, respectively, near their forward ends, whereby the extension tube can be screwed rearwardly into engagement with the seating at the firearm muzzle after the barrel attachment has been located with respect to the bayonet stud; and means for locking the blank firing attachment in position on the firearm comprising a locking member mounted on the screw-thread of the extension tube, forward of the barrel attachment, and having a longitudinally slotted, internally threaded, hollow stem extending rearwardly around said screwthread, the barrel attachment having a conical recess formed in the forward end thereof into which the stem can be screwed rearwardly, by rotation of the locking member, whereby the stem is compressed radially onto the extension tube to lock the attachment in position.

8. A blank firing attachment as claimed in claim 7 for use on a firearm fitted with a flash hider, wherein the extension tube is adapted to extend internally of the flash hider and the barrel attachment is adapted to be fitted over the flash hider.

9. A blank firing attachment for mounting on the muzzle of a firearm having a barrel when firing blank ammunition, comprising an extension tube in which is incorporated a constriction for increasing the gas pressure in the barrel when firing blank ammunition; a barrel attachment for attaching the extension tube to the muzzle of the firearm in alignment with the bore thereof: and means for locking the blank firing attachment in position on the firearm including a sleeve slidably mounted on the extension tube but restrained from rotation relative thereto, and located forward of the barrel attachment; cooperating teeth on the sleeve and the barrel attachment, respectively; and a spring acting upon said sleeve, when the attachment is in position on the firearm, to urge said sleeve to a position in which the teeth are in engagement, said teeth being capable of disengagement by moving the sleeve against the spring to screw the extension tube into or out of the barrel attachment.

10. A blank firing attachment for mounting on the muzzle of a firearm when firing blank ammunition, the firearm having a barrel and a bayonet stud adjacent the muzzle, said attachment acomprising an extension tube in which is incorporated a constriction for increasing the gas pressure in the barrel when firing blank ammunition; a barrel attachment for attaching the extension tube to the muzzle of the firearm in alignment with the bore thereof; and means for locking the blank firing attachment in position on the firearm; the extension tube having a cross-pin extending transversely across the forward end of its bore to provide the constriction, the ends of which pin protrude outwardly from the tube; and the barrel attachment comprising a channel shaped member which is pivoted at its forward end upon the ends of the crosspin, a bridge block extending across the open side of the rear end of the channel shaped member, between which block and the channel shaped member the barrel of the firearm is inserted, and a locking screw mounted in said bridge block and extending inwardly and forwardly relative to the axis of the barrel, which locking screw can 1 I be screwed into engagement with the rear face of the bayonet stud to lock the attachment in position.

11. A blank firing attachment for mounting on the muzzle of a firearm when firing blank ammunition, the firearm having a barrel and a rearwardly facing surface fixed relative to and adjacent the muzzle, comprising an extension tube having a constriction near its forward end for increasing the gas pressure in the barrel when firing blank ammunition; a barrel attachment of generally trough like form for attaching the extension tube to the muzzle of the firearm in alignment with the bore thereof; the barrel attachment having a complete tubular portion constituting the forward end thereof; means located at the rear end of the barrel attachment for engaging the rearwardly facing surface; cooperating screw-threads on, respectively, the outer surface of the extension tube, a short distance from its forward end, and the inner surface of the complete tubular portion of the barrel attachment, whereby the extension tube can be screwed into its position after the barrel attachment has been located on the firearm, the extension tube having a portion of smaller diameter than its threaded portion, the screw-threads being capable of disengagement to bring the threaded portion of the barrel attachment into register with the smaller diameter portion of the extension tube thereby permitting relative articulation of the barrel attachment and the extension tube to facilitate attachment to the firearm; means for locking the blank firing attachment in position on the firearm; a locking sleeve slidably mounted on the extension tube forward of the barrel attachment and restrained from rotation relative to the extension tube; coacting, positive engagement means upon the locking sleeve and the barrel attachment for preventing, when engaged, relative rotation therebetween; and a spring acting upon said sleeve to urge said engagement means into engagement the engagement means being releasable by movement of the sleeve against the spring to screw the extension tube into or out of the barrel attachment.

12. A blank firing attachment as claimed in claim 11 wherein the positive engagement means comprises cooperating rings of ratchet teeth carried respectively on the rear face of the locking sleeve and the forward end face of the barrel attachment.

13. A blank firing attachment as claimed in claim 11 wherein the positive engagement means comprises a longitudinally projecting pin and a cooperating ring of sockets carried, the one by the rear face of the locking sleeve and the other by the forward end face of the barrel attachment.

14. A blank firing attachment as claimed in claim 11 wherein the constriction is provided by a cross-pin extending transversely across the bore of the extension tube.

15. A blank firing attachment as claimed in claim 11 wherein the extension tube comprises a thick walled tubular casing sufficiently robust to withstand, without breaking, the impact of a bullet; a deformable arrestor member located Within said casing and arranged to deform on im pact of a bullet therewith to absorb bullet energy and to prevent egress of the bullet from the extension tube; and a tubular duct extending rearwardly from the arrestor member to connect with the firearm bore.

16. A blank firing attachment as claimed in claim 11 wherein the extension tube comprises a thick walled, tubular casing having a rearwardly facing, internal shoulder connecting a narrow forward portion and a wider rearward portion of its bore; a tubular arrestor located within the wider rearward portion of the bore of the casing, abutting said shoulder, the bore of the arrestor being generally of considerably less than firearm bore diameter and having a narrower forward portion which constitutes the constriction; and a tubular duct, whose forward end is located within the casing, extending rearward from the arrestor to provide a connection with the firearm muzzle, the bore of said duct being smaller than that of the firearm but larger than that of the arrestor,

H which is incorporated a constriction for increasing the whereby a bullet fired from the firearm to which the attachment is fitted is first subjected to some swaging by its passage through the duct, whereafter its impact with the arresor causes deformation of both arrestor and bullet to absorb the bullet energy and block its egress from the extension tube, the thickwalled casing being sufficiently robust to withstand the impact without breaking.

17. A blank firing attachment as claimed in claim 16 wherein the arrestor has a conical nose which abuts the shoulder in the casing, leaving an annular space therebetween to assist the deformation of the arrestor.

18. A blank firing attachment for mounting on the muzzle of a firearm when firing blank ammunition, the firearm having a barrel and a bayonet stud adjacent the muzzle, said attachment comprising an extension tube in gas pressure in the barrel when firing blank ammuni tion; a cross-pin extending transversely across the bore of the extension tube and constituting the constriction, the ends of the pin protruding outside the tube; an external screw-thread on the outer surface of the extension tube rearward of the pin; a barrel attachment of generally channel form for attaching the extension tube to the muzzle of the firearm in alignment with the bore thereof, the barrel attachment having formed in the rear end thereof a slot for engagement with the bayonet stud; a transverse wall across the forward end of the barrel attachment in which is formed a circular orifice larger than the cross section of the extension tube which extends therethrough and along the channel of the barrel attachment; and means for locking the blank firing attachment in position on the firearm including an internally threaded bush mounted on the screw thread of the extension tube and located in the circular orifice of the transverse wall of the barrel attachment; a radial flange on said bush which bears against the rear face of said transverse wall; a U-shaped member having a rear leg bored to accommodate the extension tube and located within the channel of the barrel attachment and against the rear face of the bush, and a forward leg also bored to accommodate the extension tube and located around the tube forward of the bush, the perimeter of the bore of this forward leg being notched for engagement with the protruding ends of the cross-pin; a helical spring coaxial with the extension tube and in compression between the forward face of the transverse wall of the barrel attachment and the forward leg of the U-shaped member, urging said member forward to a position in which the aforesaid notches engage the ends of the cross-pin to prevent relative rotation between the extension tube and the barrel attachment for locking the attachment in position; and a sleeve mounted slidably on the forward end of the extension tube but restrained from rotation relative thereto which sleeve engages the forward leg of the U-shaped member whereby the latter can be moved rearward against the spring to disengage it from the cross-pin and to screw the extension tube into its position relative to the firearm muzzle after locating the barrel attachment on the bayonet stud.

References Cited UNITED STATES PATENTS 606,115 6/1898 Benet 89-14 1,487,312 3/1924 Bull 89l4 2,447,205 8/ 1948 Powell 89-14 2,668,479 2/1954 Batten 8914 2,805,602 9/1957 Moore 8914 3,076,280 2/ 1963 Bervoets 42-86 3,137,204 6/1964 Harvey 89-l4 FOREIGN PATENTS 1,255,451 1/1961 France.

BENJAMIN A. BORCHELT, Primary Examiner,

US. Cl. X.R. 42 -79 

